title: RhoG protein regulates glycoprotein VI-Fc receptor γ-chain complex-mediated platelet activation and thrombus formation.
abstract: We investigated the mechanism of activation and functional role of a hitherto uncharacterized signaling molecule, RhoG, in platelets. We demonstrate for the first time the expression and activation of RhoG in platelets. Platelet aggregation, integrin αIIbβ3 activation, and α-granule and dense granule secretion in response to the glycoprotein VI (GPVI) agonists collagen-related peptide (CRP) and convulxin were significantly inhibited in RhoG-deficient platelets. In contrast, 2-MeSADP- and AYPGKF-induced platelet aggregation and secretion were minimally affected in RhoG-deficient platelets, indicating that the function of RhoG in platelets is GPVI-specific. CRP-induced phosphorylation of Syk, Akt, and ERK, but not SFK (Src family kinase), was significantly reduced in RhoG-deficient platelets. CRP-induced RhoG activation was consistently abolished by a pan-SFK inhibitor but not by Syk or PI3K inhibitors. Interestingly, unlike CRP, platelet aggregation and Syk phosphorylation induced by fucoidan, a CLEC-2 agonist, were unaffected in RhoG-deficient platelets. Finally, RhoG(-/-) mice had a significant delay in time to thrombotic occlusion in cremaster arterioles compared with wild-type littermates, indicating the important in vivo functional role of RhoG in platelets. Our data demonstrate that RhoG is expressed and activated in platelets, plays an important role in GPVI-Fc receptor γ-chain complex-mediated platelet activation, and is critical for thrombus formation in vivo.
authors.affiliation: Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
authors.forename: Soochong
authors.initials: S
authors.lastname: Kim
authors.affiliation: Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
authors.forename: Carol
authors.initials: C
authors.lastname: Dangelmaier
authors.affiliation: Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
authors.forename: Dheeraj
authors.initials: D
authors.lastname: Bhavanasi
authors.affiliation: Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
authors.forename: Shu
authors.initials: S
authors.lastname: Meng
authors.affiliation: Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140.
authors.forename: Hong
authors.initials: H
authors.lastname: Wang
authors.affiliation: Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Department of Anatomy and Cell Biology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140. Electronic address: goldfinger@temple.edu.
authors.forename: Lawrence E
authors.initials: LE
authors.lastname: Goldfinger
authors.affiliation: Department of Physiology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Sol Sherry Thrombosis Research Center, Temple University School of Medicine, Philadelphia, Pennsylvania 19140; Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140. Electronic address: spk@temple.edu.
authors.forename: Satya P
authors.initials: SP
authors.lastname: Kunapuli
mesh_terms: D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000925:Anticoagulants / Q000494:pharmacology; D002352:Carrier Proteins / Q000494:pharmacology; D003435:Crotalid Venoms / Q000494:pharmacology; D005260:Female; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D037181:Lectins, C-Type / Q000235:genetics / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D009842:Oligopeptides / Q000494:pharmacology; D010455:Peptides / Q000494:pharmacology; D010766:Phosphorylation / Q000187:drug effects / Q000235:genetics; D010974:Platelet Aggregation; D010980:Platelet Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D011134:Polysaccharides / Q000494:pharmacology; D011494:Protein Kinases; D011961:Receptors, Fc / Q000235:genetics / Q000378:metabolism*; D013873:Thionucleotides / Q000494:pharmacology; D013927:Thrombosis / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000925:Anticoagulants; C529518:CLEC-2 protein, mouse; C104778:CLEC2B protein, human; D002352:Carrier Proteins; D003435:Crotalid Venoms; D037181:Lectins, C-Type; D008562:Membrane Glycoproteins; D009842:Oligopeptides; D010455:Peptides; D010980:Platelet Membrane Glycoproteins; D011134:Polysaccharides; D011961:Receptors, Fc; C489577:Rhog protein, mouse; D013873:Thionucleotides; C455901:alanyl-tyrosyl-prolyl-glycyl-lysyl-phenylalanine; C435908:collagen-related peptide; C098341:platelet membrane glycoprotein VI; C075397:RHOG protein, human; C002480:methylthio-ADP; C028890:convulxin; D000244:Adenosine Diphosphate; C007789:fucoidan; D011494:Protein Kinases; D020558:GTP Phosphohydrolases; D020741:rho GTP-Binding Proteins
keywords: Collagen; Fc Receptors; Glycoprotein VI; Platelets; Rho GTPases; Thrombosis